South Carolina’s warped public display of its white-supremacist history confronts South Carolinians, white and black, with a stark message about who rules the state.

Eric Foner is a professor of history at Columbia University and the author of numerous books on the Civil War and Reconstruction.

Dylann Roof, the accused murderer of nine men and women in the Emanuel AME Church in Charleston, is clearly a disturbed individual. Yet the language he drew on to justify his crime demonstrates the enduring power of historical myths and memories. Before opening fire on his victims, Roof reportedly explained his actions by saying, “You are raping our women and taking over the country.” This supposed need to save white women from black rapists has deep historical roots. It was invoked to legitimate the violent overthrow of Reconstruction, the nation’s first experiment in interracial democracy. Black victims of lynching in South Carolina and elsewhere were often described as rapists, even though, as the anti-lynching crusader Ida B. Wells pointed out, in nearly every case the accusation was a “bare lie.” A black rapist was a pivotal figure in The Birth of a Nation, the 1915 film that glorified the Ku Klux Klan. Claude Bowers’s influential 1929 history of the post–Civil War years, The Tragic Era, described rape in the South as the product of the political rights blacks achieved during Reconstruction—a ludicrous statement in view of the countless black women who suffered sexual assault under slavery. Roof’s complaint that blacks were “taking over” the state echoes justifications for racist violence during and after Reconstruction and the disfranchisement of black voters in the 1890s.

Roof has a sense of history, warped though it may be. He claims to have read “hundreds” of slave narratives, all demonstrating, to his satisfaction, how benevolently slaves were treated—an idea long discredited by historians, but still encountered on white-supremacist websites and conservative talk-radio shows. He had himself photographed not only with the flags of the Confederacy, apartheid South Africa, and Rhodesia, during its short-lived period of independence under white domination, but at a slave plantation. He knows enough to have chosen the Emanuel Church, long a vital center of black life and politics, to strike his blow against the black community.

Emanuel was the place of worship not only of Denmark Vesey, who plotted a slave insurrection in Charleston in 1822, but also of the Reverend Richard H. Cain, who occupied Emanuel’s pulpit during Reconstruction. Like his successor the murder victim Clementa Pinckney, Cain used the church as a springboard to public service, including a term in the State Senate, where he worked to provide former slaves with access to land. Later, as a member of Congress, Cain rebuked a white Representative who referred to slavery as a civilizing institution for black “barbarians” (not unlike Roof’s outlook). His colleague’s concept of civilization, Cain replied, seemed to amount to little more than “the lash and whipping post.” Unlike Pinckney, Cain did not fall victim to violence, but he and his family lived “in constant fear” and his home was guarded day and night by armed men.

I have taught in South Carolina and lectured in the state numerous times. I have unfailingly been treated with courtesy and respect. Roof does not speak for all the white people in the state. Nonetheless, South Carolina has never really come to terms with its tortured history. Here are a few highlights of the state’s extreme pro-slavery, white-supremacist past. In 1776, South Carolina delegates to the Continental Congress forced Thomas Jefferson to remove a clause condemning slavery from the Declaration of Independence. In 1787, South Carolinians were primarily responsible for the Constitution’s fugitive slave clause and provision allowing the importation of slaves from abroad to continue for 20 additional years. Until 1860, a tight-knit coterie of plantation owners controlled the state; they did not even allow the white citizens to vote in presidential elections (the legislature chose the state’s members of the Electoral College).

Before the Civil War, South Carolina was one of two states, along with Mississippi, where nearly a majority of white families owned slaves, and had the largest black majority in its population (nearly 60 percent in 1860). This combination produced a unique brand of extremism in defense of slavery. The state was the birthplace of nullification, the first to secede, and the site of the first shot of the Civil War. During Reconstruction, black Carolinians enjoyed a brief moment of civil equality and genuine political power, but this ended with a violent “Redemption,” followed by decades of Jim Crow. More recently, South Carolina led the Southern walkout from the 1948 Democratic National Convention to protest a civil-rights plank in the party’s platform, and supported its native son, Strom Thurmond, who ran as the “Dixiecrat” candidate for president. In 1964, it was one of five states of the Deep South to vote for Barry Goldwater, paving the way for the Republicans’ “Southern strategy” of appealing to white resentment against black civil-rights gains....